How to Use Diodes in an OP Amp Circuit

Operational amplifiers are typically housed in dual inline packaging.

Operational amplifiers (or op-amps, for short) are integrated circuits which are often used in alternating current amplifier circuits. However, an operational amplifier, when coupled with a pair of switching diodes, can be used to create an electronic circuit called a pulse generator.

Things You'll Need

• 12-volt DC power supply
• 1 LM158 Operational amplifier
• 1 1 pF dielectric (non-polarized) capacitor
• 2 1N914 diodes
• 4 100kΩ resistors
• 1 1MΩ resistor
• Electrical wire
• Electrical pliers
• Soldering iron
• Electronic (rosin core) solder

Instructions

1. Cut five lengths of wire, and strip 1/2 inch of insulation from the ends of each wire. Twist together one of the leads each from the first, second and third 100kΩ resistors with the op-amp noninverting input terminal (pin 3). Solder the connection.

2. Twist together the first diode cathode lead (which is marked with a line across the diode) with the anode lead from the second diode. Attach one end of the first wire to this twisted lead pair, and solder the electrical connection.

3. Twist together the free end of the first wire jointly with the free end of the first 100kΩ resistor and the op-amp output lead (pin 1). Solder this connection.

4. Twist together the anode lead from the first diode with one of the leads from the 1MΩ resistor, and solder the connection. Twist together the cathode lead from the second diode together with one of the leads from the fourth 100kΩ resistor, and solder the connection.

5. Twist together one end of the second wire jointly with the free leads from the fourth 100kΩ resistor and the1MΩ resistor, and solder the connection. Twist together the free end of the second wire jointly with one of the capacitor leads and the op-amp inverting input (pin 2). Solder this connection.

6. Twist together one end of the third wire jointly with the free capacitor lead and the free lead from the second 100kΩ resistor. Solder this joint. Attach the free end of the third wire to the negative terminal on the power supply.

7. Twist together one end of the fourth wire with the op-amp "V+" power input (pin 8), and solder the connection. Twist together one end of the fifth wire with the op-amp "Ground" input (pin 4), and solder the connection. Attach the free end of the fourth wire to the positive terminal on the power supply. Attach the free end of the fifth wire to the negative terminal on the power supply.

Tips & Warnings

• The input signal lead can be attached to the free lead on the third 100kΩ resistor. The output signal lead can be attached to the op-amp output (pin 1).

References

• "Georgia State University: Op-Amp Varieties"
• "Solarbotics: 1N914 Fast Switching Diode"
• "National Semiconductor: LM158/LM258/LM358/LM2904 Low Power Dual Operational Amplifiers"